Molecular Tectonics of Four-Connected Network Topologies by Regulating the Ratios of Tetrahedral and Square-Planar Building Units

Assembly of the 4-connected building units leads to three three-dimensional frameworks, {[Cd­(TPPBDA)­(OH)2]·2H2O·4DMA}n (1), {[Cd­(TPPBDA)1/2(tpdc)]·DMF}n (2), and {[Zn­(TPPBDA)1/2(bpdc)]·3H2O·3DMF}n (3) (TPPDBA = N,N,N′,N′-tetrakis­(4-(4-pyridine)-phenyl) biphenyl-4,4′-diamine, H2tpdc = 4,4″-dicarboxyl-(1,1′,3′,1″)-terphenyl), H2bpdc = biphenyldicarboxylic acid, DMF = N,N-dimethylformamide, DMA = N,N-dimethylacteamide), which are based on different ratios of tetrahedral (T) and square-planar (S) building units. For compound 1, T and S nodes are in the ratio of 1:1, which is the feature of pts. While T/S is 2:1 in compound 2 to form a bbf framework, for compound 3, the TPPBDA ligand and the metal center are both in tetrahedral configuration, which constructs a dia net with the ratio of 2:0 (T/S). In addition, the compound 2 exhibits high selectivity for CO2 over CH4, showing a hysteretic sorption–desorption loop.